Based on toxicology studies, benzimidazoles such as Fenbendazole, Mebendazole or Albendazole seem to be safe drugs.
However, a drug without no side-effects does not exist. No scientific data reports significant adverse reactions from taking fenbendazole. Despite the fact, there are anecdotal reports of potential toxicity:
- Up to 5 % of people can experience stomach discomfort or diarrhea when taking large quantities of fenbendazole with no breaks.
- People with severe liver or kidney failure have lower medication excretion rates, therefore, fenbendazole can accumulate and cause unexpected side-effects. Doses should be divided accordingly in this situation.
The protocol was designed to keep the liver in optimal health, therefore the schedule 3 days on, 4 days off is suggested.